After the Industrial Revolution, humans established modern society while consuming huge amounts of fossil fuel, which increases a carbon dioxide concentration in the air, and the increase of the carbon dioxide concentration is further promoted by environmental destruction such as deforestation or the like. Since global warming is caused by an increase in greenhouse gases such as carbon dioxide, Freon, or methane in the air, it is important to decrease the concentration of carbon dioxide that significantly contributes to the global warming, and various researches into emission regulations, stabilization, or the like, of carbon dioxide have been conducted around the world.
Among them, a copolymerization reaction of carbon dioxide and an epoxide found by Inoue et al. has been expected to be a reaction capable of solving the global warming problem, and research has been actively conducted in view of using carbon dioxide as a carbon source as well as in view of chemical fixation of carbon dioxide. Particularly, recently, a poly(alkylene carbonate) resin formed by polymerization of carbon dioxide and an epoxide has been spotlighted as a kind of biodegradable resin.
Various catalysts for preparing this poly(alkylene carbonate) resin have been studied and suggested in the past, and as a representative catalyst, a zinc dicarboxylate-based catalyst such as a zinc glutarate catalyst in which zinc and a dicarboxylic acid are bonded to each other, or the like, has been known.
The zinc dicarboxylate-based catalyst as described above, representatively, the zinc glutarate catalyst, is formed by reacting a zinc precursor and a dicarboxylic acid such as glutaric acid, or the like, with each other, and has a fine crystalline particle shape. However, it was difficult to control the zinc dicarboxylate-based catalyst having the crystalline particle shape as described above to have a uniform and fine particle size during a preparation process. The existing zinc dicarboxylate-based catalyst has a particle size of a nanometer scale, but an aggregate having an increased particle size and a decreased surface area is formed in a medium by aggregation of catalyst particles such that at the time of preparing the poly(alkylene carbonate) resin, the activity may be deteriorated.
Therefore, there is often a case in which the existing known zinc dicarboxylate-based catalyst has a relatively large particle size and a non-uniform particle shape. Therefore, in the case of performing a polymerization process for preparing a poly(alkylene carbonate) resin using the zinc dicarboxylate-based resin, a sufficient contact area between a reactant and the catalyst is not secured, such that polymerization activity may not be sufficiently exhibited. In addition, there is often a case in which the activity of the existing zinc dicarboxylate-based catalyst itself is also not sufficient.
Further, in the case of the zinc dicarboxylate-based catalyst, it is not easy to disperse and control the catalyst particles in a reaction solution due to non-uniformity of the particle size.